1. Field of the Invention
The present invention relates to an apparatus for folding over the opposed longitudinal edges of a pair of fabric pieces or panels of an article and then sewing the folded longitudinal edges of the panels to a continuous slide fastener chain along the outer longitudinal edges of a pair of stringer tapes of the slide fastener chain having a row of interengaged coupling elements.
2. Description of the Prior Art
In the manufacture of a slide fastener sewn to the opposed longitudinal edges of a pair of fabric pieces or panels of an article, such as left and right front panels of a garment, or front and rear panels of a bag, the opposed longitudinal edges of the panels are folded over and the thus folded longitudinal edges of the panels are attached by sewing to the outer longitudinal edges of a pair of stringer tapes of a continuous slide fastener chain. Several examples of known apparatus used for performing the above-mentioned sewing operation are disclosed in U.S. Pat. Nos. 2,131,250, 2,977,904, 3,286,669, 4,674,422, 4,996,933 and 5,070,799. It is common to all the disclosed apparatus that a pair of parallel juxtaposed fabric pieces or panels of an article and a continuous slide fastener chain having a row of interengaged coupling elements are supplied concurrently to a double needle sewing machine. The sewing machine operates to attach the panels to the slide fastener chain by sewing the opposed longitudinal edges of the panels to the outer longitudinal edges of a pair of stringer tapes of the slide fastener chain. An edge-folding means is disposed upstream of the sewing machine and extends longitudinally along the path of supply of the panels for progressively folding back the opposed longitudinal edges of the panels as the panels are advanced toward the sewing machine. With the edge-folding means thus provided, the opposed longitudinal edges of the panels are supplied in a folded condition to the sewing machine. The thus folded longitudinal edges are then sewn to the outer longitudinal edges of the stringer tapes by the sewing machine.
The edge-folding means generally has a pair of spiraled or convoluted guide grooves extending from the upstream side to the downstream side of the path of feed of the panels. At an upstream end of the edge-folding means, the leading ends of the respective panels are set such that opposed longitudinal edges of the panels are received in the guide grooves. Then, the panels are advanced toward the sewing machine. As the panel advances, the opposed longitudinal edges received in the guide grooves are bent downwards, then progressively folded back toward the underside of the panels, and finally fully folded over in such a manner as to form a two-ply or folded longitudinal edges.
All the known apparatus except one disclosed in U.S. Pat. No. 4,674,422 have no means for guiding or directing the opposed longitudinal edges of the panels toward the edge-folding means. The edge-folding operation fully relies upon a pulling force produced during the advancing movement of the panels and hence is severely influenced by the flexibility of material of the panels. For instance, when the panels are relatively hard and inflexible, the opposed longitudinal edges of the panels being advanced are insufficiently drawn into the guide grooves in the edge-folding means. Conversely, when the panels are relatively soft and highly flexible, the opposed longitudinal edges of the panels are excessively drawn into the guide grooves in the edge-folding means. In either case, accurately folded longitudinal edges cannot be produced by the edge-folding means. Formation of the inaccurately folded longitudinal edges results in the panels inaccurately sewn to the slide fastener chain.
The apparatus disclosed in U.S. Pat. No. 4,674,422 includes a drive means for guiding the opposed longitudinal edges of a pair of fabric pieces or panels toward the edgefolding means. However, the drive means is only active on a leading end portion of the opposed longitudinal edges. Accordingly, those portions of the opposed longitudinal edges which extend parallel to and along the edge-folding means are freed from the action of the drive means. The apparatus further has a material directing means disposed adjacent to the edge-folding means. The material directing means is frictionally engageable with the panels for directing the opposed longitudinal edges of the panels toward the edge-folding means. However, since the material directing means is only operative in response to the advancing movement of the panels, the edge guiding effect of the material directing means is severely influenced by the flexibility of material of the panels. Accordingly, depending on the material of the panels, inaccurately folded longitudinal edges of the panels are likely to be produced in the same manner as described above. In addition, the apparatus is per se complicated in construction and uneasy to operate.